GNU C-Graph is a tool for visualizing the mathematical operation of convolution underlying natural phenomena susceptible to analysis in terms of engineering signals and systems theory. "C-Graph" is an abbreviation for "Convolution Graph". The package is derived from the BSc. Honours dissertation in Electrical Engineering "Interactive Computer Package Demonstrating: Sampling Convolution and the FFT", Adrienne Gaye Thompson, University of Aberdeen (1983).

The package computes the linear convolution of two signals in the time domain then compares their circular convolution by demonstrating the convolution theorem. Each signal is modelled by a register of discrete values simulating samples of a signal, and the discrete Fourier transform (DFT) computed by means of the Fast Fourier Transform (FFT).

GNU C-Graph is interactive, prompting the user to enter character or numerical values from the keyboard, dispensing with the learning curve for writing code. The software will be useful to students of signals and systems theory.

C-Graph is written in contemporary Fortran. You can find pre-GNU development versions at: